For greater convenience and portability many modern electrical appliances and consumer products may be operated to draw electric current from dry cells (commonly referred to as "batteries") of standard size and electrical performance. For convenience and economy, various rechargeable, or secondary, batteries have been developed. A number of chargers, operating off of household current, have been developed to charge those rechargeable batteries. Due to differences in chemistry, however, nonrechargeable, or primary, batteries such as zinc-carbon or manganese dioxide alkaline batteries may leak, discharge gasses, or in some cases rupture, if subjected to a recharging current. Thus, for safety purposes, battery charges should be provided with a means for discriminating between batteries which may be safely recharged therein, and those which may not.
Several prior art disclosures suggest different means for discriminating between batteries which should and should not be charged, including:
______________________________________ Country Pat. No. Inventor Year of Issue ______________________________________ U.S.A. 3,391,321 Ota 1968 U.S.A. 3,579,075 Floyd 1971 U.S.A. 4,147,838 Leffingwell 1979 U.S.A. 4,303,182 Yeh 1983 U.S.A. 4,489,268 Beachy 1984 U.S.A. 4,577,144 Hodgman et al. 1986 U.S.A. 4,577,145 Mullersman 1986 U.S.A. 4,602,202 Mundschenk et al. 1986 U.S.A. 4,628,243 Hodgman et al. 1986 U.S.A. 4,645,996 Toops 1987 U.S.A. 4,816,735 Cook et al. 1989 U.S.A. 5,038,093 Edwards et al. 1991 U.S.A. 5,057,761 Felegyhazi et al. 1991 U.S.A. 5,108,847 Edwards et al. 1992 ______________________________________
Certain known chargers prevent battery charging accidents by providing the chargers with electrical circuits capable of distinguishing between batteries which should and should not be charged. Distinguishing electrical circuits within chargers are undesirable due to the extensive effort required to develop them, and the relative difficulty and high cost of manufacturing such circuits and batteries therefor.
Other known battery chargers provide compatible rechargeable batteries with predetermined features such as specialized cathode or anode terminals, recesses, keyways, or conductive rings disposed about the battery that enable the battery charger to discriminate between batteries that should and should not be charged.
U.S. Pat. No. 3,391,321 discloses a battery charger having sliding contacts for engaging the positive terminals of batteries charged therein.
U.S. Pat. No. 3,579,075 discloses a battery charger for charging AA, C or D size batteries. The battery charger uses a combination of positive contact recesses disposed in the sidewall thereof and battery support means disposed therein to discriminate between batteries of different sizes. Each positive contact recess is positioned at a particular height above the battery support means to receive a battery of a predetermined size. Depending on the size battery inserted in the charger, the battery engages only the positive and negative contacts of the battery charging circuit to which its size corresponds. Thus, the charger supplies varying amounts of charging current to AA, C, and D size batteries. The charger does not discriminate between primary and secondary batteries, however.
U.S. Pat. No. 4,147,838 discloses a rechargeable battery having a special charging contact. The rechargeable battery is used in a compatible appliance, the appliance having the battery charger incorporated therein. The charger supplies charging current only to rechargeable batteries having the special charging contact. The special contact is physically distinct and separate from the two power terminals of the battery.
U.S. Pat. No. 4,403,182 discloses a battery charger having means for preventing the charging of batteries placed in an improper, reverse orientation therein. Such means comprise a support structure for accepting and holding batteries, and contact elements disposed at different radial offsets in respect of the central longitudinal axes of cylindrical batteries placed therein, the offsets being determined by the size of the battery to be charged.
U.S. Pat. No. 4,577,144 discloses a charger capable of distinguishing rechargeable batteries from non-rechargeable batteries. This charger incorporates a sensing means in the charger for sensing at least one inherent parameter, such as the low frequency impedance of a rechargeable battery demonstrated during charging. Such a parameter has a value for secondary batteries that is distinctive from its value for primary batteries.
U.S. Pat. No. 4,577,145 teaches a charging system having means to distinguish between rechargeable and non-rechargeable batteries. The charger establishes an electromagnetic field proximate to the battery, wherein a circuit within a secondary battery, but not a primary battery, enters a resonant condition in response to the electromagnetic field, and the resonant condition is sensed by the charging system to switch the system from a non-charging mode to a charging mode.
U.S. Pat. Nos. 4,489,268, 4,602,202, 4,628,243, 4,645,996, 4,816,735, 5,038,093, 5,057,761, and 5,108,847 disclose chargers adapted for rechargeable batteries having a certain predetermined feature that must be present for the battery to be charged.
In U.S. Pat. No. 4,489,268, the predetermined feature is an annular charging terminal on the cylindrical portion of the battery. The charger has a cooperating contact that functions with rechargeable batteries having this annular charging terminal, thus precluding charging of primary batteries.
U.S. Pat. No. 4,602,202 discloses a predetermined feature that is a connector for attachment to the terminals of primary or secondary 9-Volt batteries, the connector having an actuating rod therein. Rechargeable 9-Volt batteries equipped with the connector may receive charging current from a charging circuit disposed in an appliance containing both the battery and the circuit. Cooperative action of the actuating rod and a compatible recess therefor disposed in the rechargeable battery permit the charging circuit to energize the battery. Primary batteries not having the recess cannot receive charging current from the charging circuit, as they do not contain the required recess for energizing the charging circuit.
The predetermined feature taught in the U.S. Pat. No. 4,628,243 is a conductive band that serves to bridge a pair of contacts when the battery is placed in the charger. When the contacts are electrically bridged, charging current is delivered to the battery terminals.
The predetermined feature taught in U.S. Pat. No. 4,645,996 is an elongated positive terminal that protrudes a greater distance above the top cover of the battery than is permitted by ANSI standards for primary or secondary batteries. A compatible battery charger has a contact for engaging only the elongated positive terminals of the batteries of the described invention. Because the battery having the elongated positive terminal substantially exceeds ANSI specifications for overall cell height, it cannot be used in most devices designed to accept cylindrical batteries cells of standard dimensions.
U.S. Pat. No. 4,816,735 discloses a battery charger having slotted keyway means for excluding therefrom batteries not having positive terminals of a minimum diameter of 0.240 inches. The excluding means is a slotted keyway sized to accept only C or D size batteries having positive terminal diameters of 0.240 inches (or less). Table 1, infra, however, shows that an Eveready C size primary alkaline battery would be accepted and charged by the battery charger of the '735 patent, even though that battery is neither intended, nor designed, to be recharged.
In U.S. Pat. Nos. 5,038,093 and 5,108,847, the predetermined feature is a first positive battery terminal forming an outer annulus for engaging a fast charging contact on a compatible battery charger. The first terminal is disposed at a radial distance from the longitudinal axis of the battery that is greater than that of conventional primary or secondary batteries. The compatible battery charger provides slow charging current to conventional primary or secondary batteries, or to the battery of the described invention through a second positive battery terminal forming an inner, indented recess. Only a battery having a first positive terminal forming an outer annulus will be fast charged by the compatible battery charger, however.
In U.S. Pat. No. 5,057,761, a battery charger is disclosed having means of distinguishing between batteries capable of being fast charged and batteries that should be slow charged. Fast charge batteries typically have positive terminals that are smaller in diameter than those of slow charge batteries, but that nonetheless fall within ANSI specifications for round cell positive cathode terminal width and height.
In the '761 patent, the positive terminal of a fast charge battery is inserted through a rectangular opening in the positive charger contact, the terminal protruding through the contact opening far enough to further engage and close a switching means for actuating a fast charge charging circuit. Slow charge batteries having larger diameter positive cathode terminals cannot be inserted through the opening, and therefore cannot engage the switching means. As a result, slow charge batteries are charged at a slower charge rate.
The '761 patent discloses a battery charger designed to accept and charge both slow charge nickel cadmium batteries and fast charge nickel cadmium batteries. Slow charge nickel cadmium batteries are typically manufactured in accordance with ANSI standards for round cell positive terminal height and diameter. Thus, the battery charger of the '761 patent will accept and charge conventional primary alkaline or zinc-carbon cylindrical batteries of the AAA, AA, C and D sizes at the slow charge rate because those batteries are also manufactured in accordance ANSI standards for positive terminal height and width.
The prior art shows that many ways have been found to construct a battery charger that will charge only batteries having a certain predetermined feature, none of which, however, is entirely satisfactory from the combined standpoints of safety, cost, manufacturability, and ease of use.
More particularly, none of the battery charging systems known heretofore is capable of discriminating on a low cost dimensional basis alone between batteries that should be charged, and primary and secondary batteries that should not be charged.
What is needed is a battery charger system that does not permit any undesired batteries to be charged therein. In the event that the consumer accidentally places a battery not having a predetermined feature into the charger, it is desirable that no charging current be delivered to such a battery.
What is also need is a battery charger system that may be manufactured and sold to consumers at low cost. Chargers having sensing or switching means for distinguishing between rechargeable and non-rechargeable batteries require more complicated electrical circuitry, resulting in increased charger cost. Chargers adapted for use with secondary batteries having separate charging terminals result in a more expensive battery. Although batteries are available in a variety of sizes, each having different current capabilities, it is too costly to require a different charger for each size battery, or to manufacture a charger adapted to charge batteries having different current capabilities at different rates, or for varied durations.
What is further needed is a battery charger system that is easy to use. It is desirable to produce a battery charger system that is simple to use and consumer-friendly. The charger should be designed so that the consumer may place the battery into the charger with ease.
It is therefore an object of the present invention to provide a charger that is capable of recharging the batteries only if the batteries have a predetermined feature.
It is another object of the present invention to provide a charger that can accommodate the several different sizes, and charge the battery without regard to the different current capabilities.
It is yet another object of the present invention to provide a charger that is simple to use and consumer-friendly.
It is still yet another object of the present invention to provide a charger that does not provide a charging current to primary or secondary batteries not having the predetermined feature, but which are accidentally placed in the charger.
It is a further object of the present invention to provide a charger that can accommodate a variety of battery sizes.
It is further object yet of the present invention to provide a charger that is simple and inexpensive to manufacture.
Other objects and advantages will become apparent from the detailed description of the invention.